arXiv subjects

Ambar Ghosal

Publications and source records attributed to Ambar Ghosal.

52 records · Page 3Linked to original sources

arXiv2003

An $SU(2)_L\times U(1)_Y$ model with reflection symmetry in view of recent neutrino experimental result

We demonstrate that an $SU(2)_L\times U(1)_Y$ model with the same particle content as Standard Model(SM) and discrete reflection symmetry between second and third generation of leptons give rise to charged lepton and neutrino mass matrices which can accommodate the present solar, atmospheric, WMAP neutrino experimental results.The model predicts the value of $|U_{13}|$ which could be tested in neutrino factories and the value of the effectiv Majorana neutrino mass $ $ comes out at the lower end of the present experimental limit. Neutrino masses are generated through dim = 5 operators and the scale of which is constrained by the value of $ $. If, in future neutrino less double beta decay experiments, namely, MOON, EXO, GENIUS etc. shifts the lower bound on $ }$ by one order the present model will fail to accommodate the solar neutrino mixing angle due to LMA solution.

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arXiv2002

A texture of neutrino mass matrix in view of recent neutrino experimental results

In view of recent neutrino experimental results such as SNO, Super-Kamiokande (SK), CHOOZ and neutrinoless double beta decay $(ββ_{0ν})$, we consider a texture of neutrino mass matrix which contains three parameters in order to explain those neutrino experimental results. We have first fitted parameters in a model independent way with solar and atmospheric neutrino mass squared differences and solar neutrino mixing angle which satisfy LMA solution. The maximal value of atmospheric neutrino mixing angle comes out naturally in the present texture. Most interestingly, fitted parameters of the neutrino mass matrix considered here also marginally satisfy recent limit on effective Majorana neutrino mass obtained from neutrinoless double beta decay experiment. We further demonstrate an explicit model which gives rise to the texture investigated by considering an $SU(2)_L\times U(1)_Y$ gauge group with two extra real scalar singlets and discrete $Z_2\times Z_3$ symmetry. Majorana neutrino masses are generated through higher dimensional operators at the scale $M$. We have estimated the scales at which singlets get VEV's and M by comparing with the best fitted results obtained in the present work.

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arXiv2002

Radiatively Induced Neutrino Mass Matrix in a SUSY GUT Model with R-Parity Violation

In order to evade the proton decay which appears when the Zee model is embedded into a SUSY GUT scenario with R-parity violation, a new idea based on a discrete Z_2 symmetry is proposed. Under the symmetry Z_2, the quark and lepton mass matrices are tightly constrained. The admissible form of the radiatively-induced neutrino mass matrix is investigated.

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arXiv2001

Lepton Flavor Violating Z Decays in the Zee Model

We calculate lepton flavor violating (LFV) Z decays Z \to {e_i^\pm}e_j^\mp (i, j = e, μ, τ; i\neq j) in the Zee model keeping in view the radiative leptonic decays e_i\to e_jγ(i = μ, τ; j = e, μ; i\neq j), μdecay and anomalous muon magnetic moment (μAMM). We investigate three different cases of Zee f_{ij} coupling (A) f_{eμ}^2 = f_{μτ}^2= f_{τe}^2, (B) f_{eμ}^2 \gg f_{τe}^2 \gg f_{μτ}^2, and (C) f_{μτ}^2 \gg f_{eμ}^2 \gg f_{τe}^2 subject to the neutrino phenomenology. Interestingly, we find that, although the case (C) satisfies the large excess value of μAMM, however, it is unable to explain the solar neutrino experimental result, whereas the case (B) satisfies the bi-maximal neutrino mixing scenario, but confronts with the result of μAMM experiment. We also find that among all the three cases, only the case (C) gives rise to largest contribution to the ratio B(Z\to e^\pmτ^\mp)/B(Z\to μ^\pm μ^\mp) \simeq {10}^{-8} which is still two order less than the accessible value to be probed by the future linear colliders, whereas for the other two cases, this ratio is too low to be observed even in the near future for all possible LFV Z decay modes.

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arXiv2000

Bimaximal Neutrino Mixing in a Zee-type Model with Badly Broken Flavor Symmetry

A Zee-type neutrino mass matrix model with a badly broken horizontal symmetry SU(3)_H is investigated. By putting a simple ansatz on the symmetry breaking effects of SU(3)_H for transition matrix elements, it is demonstrated that the model can give a nearly bimaximal neutrino mixing with the ratio $Δm^2_{solar}/Δm^2_{atm} \simeq \sqrt{2} m_e/m_μ=6.7 \times 10^{-3}$, which are in excellent agreement with the observed data. In the near future, the lepton-number violating decay $Z\to μ^\pm τ^\mp$ will be observed.

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arXiv2000

A Two Parameter Texture of Nearly Bi-maximal Neutrino Mixing

We propose a texture of three generation Majorana-type neutrino mass matrix in terms of only two parameters which gives rise to nearly bi-maximal mixing angles. We also demonstrate an explicit realization of such type of neutrino mass-matrix in the context of an $SU(2)_L$$\times$$U(1)_Y$ model due to higher dimensional mass terms through the inclusion of discrete $Z_3$$\times$$Z_4$ symmetry and two extra singlet Higgs fields.

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arXiv2000

Democratic Universal Seesaw Model with Three Light Sterile Neutrinos

Based on the "democratic" universal seesaw model, where mass matrices $M_f$ of quarks and leptons f_i (f=u,d,ν,e; i=1,2,3) are given by a seesaw form M_f\simeq -m_L M_F^{-1} m_R, and m_L and m_R are universal for all the fermion sectors, and the mass matrices M_F of hypothetical heavy fermions F_i have a democratic structure, a possible neutrino mass matrix is investigated. In the model, there are three sterile neutrinos ν_{iR} which mix with the active neutrinos ν_{iL} with θ\sim 10^{-2} and which are harmless for constraint from the bib bang nucleosynthesis. The atmospheric, solar and LSND neutrino data are explained by the mixings ν_{μL} \leftrightarrowν_{τL}, ν_{eL}\leftrightarrow ν_{eR} and ν_{eL}\leftrightarrow ν_{μL}, respectively. The model predicts that Δm^2_{solar}/Δm^2_{atm} \simeq (R^2-1) m_e/\sqrt{m_μm_τ} [R=m(ν_{iR})/m(ν_{iL}) (i=1,2,3)] with \sin^{2}2θ_{atm}\simeq 1 and Δm_{LSND}^2/Δm^2_{atm} \simeq (1/4)\sqrt{m_μ/m_e} with \sin^2 2θ_{LSND} \simeq 4m_e/m_μ.

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arXiv1999

R-parity Violating Radiative Photino Decay in Supersymmetric Models

It has been shown that unless the tri-linear R-parity violating coupling $λ_{i33}$ (i = 1, 2) is small enough ($λ_{i33}<$ ${10}^{-2}$ for MSSM and ${10}^{-3}$ for GMSB model),the partial decay width of photino decaying into 'photon + $ν_{e,μ}$', both in supergravity motivated (MSSM) and gauge mediated (GMSB) supersymmetric models are larger than the partial decay width of photino decaying into 'photon + goldstino' in R-parity conserving GMSB model including one loop supersymmetric QED correction.

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arXiv1999

Bi-maximal Neutrino Mixing With SO(3) Flavour Symmetry

We demonstrate that an $SU(2)_L\times U(1)_Y$ model with extended Higgs sector gives rise to bi-maximal neutrino mixing through the incorporation of SO(3) flavour symmetry and discrete symmetry. The neutrino and the charged lepton masses are generated due to higher dimensional terms. The hierarchical structures of neutrinos and charged leptons are obtained due to inclusion of SO(3) flavour symmetry and discrete symmetry.The model can accommodate the vacuum oscillation solution of solar neutrino problem, through reasonable choice of model parameters along with the atmospheric neutrino experimental result.

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arXiv1999

Light Dirac Neutrinos In An $SU(2)_L\times U(1)_Y$ Model

Light Dirac neutrino of mass of mass of the order of few eV is obtained in an $SU(2)_L\times U(1)_Y$ model with an extended Higgs sector and right-handed neutrinos. Small neutrino mass is generated at the tree level through small effective coupling of the Dirac neutrino mass term due to soft discrete symmetry breaking. In order to remove the exact degeneracy in mass between the second and the third generation of neutrinos, one loop corrected mass terms are incorporated. The model can accommodate bi-maximal mixing scenario of neutrino which has been favoured by recent Solar and atmospheric neutrino experiments.

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arXiv1998

Radiative neutrino mass matrix for three active plus one sterile species

A simple unifying mass matrix is presented for the three active and one sterile neutrinos $ν_e$, $ν_μ$, $ν_τ$ and $ν_s$, using an extension of the radiative mechanism proposed some time ago by Zee. The total neutrino-oscillation data are explained by the scheme $ν_e \leftrightarrow ν_s$ (solar), $ν_μ\leftrightarrow ν_τ$ (atmospheric) and $ν_e \leftrightarrow ν_μ$ (LSND). We obtain the interesting approximate relationship $(Δm^2)_{atm} \simeq 2[(Δm^2)_{solar} (Δm^2)_{LSND}]^{1/2}$ which is well satisfied by the data.

hep-ph↗

arXiv1997

R parity violating contribution to $e^+e^-(μ^+μ^-)\to t{\bar c}$

In this article we consider the contribution of $R_p$ violating couplings to the process $e^+e^-(μ^+μ^-)\to t{\bar c}$ at high energy lepton collider. We show that the present upper bound on the relevant $R_p$ violating coulpings obtained from low energy measurements would produce a few hundred to a thousand top-charm events at the next linear $e^+e^-(μ^+μ^-)$ collider. Hence, it should be possible to observe the rare process at future lepton collider.

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arXiv1997

Gauge-Mediated Supersymmetry Breaking Signals in an Electron-Photon Collider

We show the usefulness of an $e^-γ$ collider with backscattered laser photons in unveiling the signatures of Gauge-Mediated Supersymmetry Breaking models, with a right selectron as the next LSP. We also show how the signal can be distinguished from the Standard Model background as well as from signals of minimal supersymmetry.

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arXiv1996

Probing Gauge-Mediated Supersymmetry Breaking Through Polarized Electron Beams in an $e^+e^-$ Collider

Using the facts that in Gauge-Mediated Supersymmetry Breaking schemes, masses of the right and the left sfermions can differ widely, and the gravitino is the Lightest Supersymmetric Particle, we show that it is possible to obtain unambiguous signatures of such schemes in a high energy $e^+e^-$ collider if one looks at the asymmetries in the cross-sections for certain final states with left-and right-polarized beams.

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arXiv1995

Degenerate Dirac Neutrinos In An ${SU(2)}_L\times {U(1)}_Y$ Model With $S_3\times Z_3\times Z_4$ Discrete Symmetry

We demonstrate that almost degenerate Dirac neutrinos of mass of few eV and transition magnetic moment of the order of ${10}^{-11}$ $μ_B$ can be obtained in an ${SU(2)}_L\times {U(1)}_Y$ model with $S_3\times Z_3\times Z_4$ discrete symmetry and appropriate Higgs fields. Transition magnetic moment of the Dirac neutrino arises from to the contribution of leptons and charged Higgs fields at the one loop level.

hep-ph↗

arXiv1995

Recent Neutrino Experiments and Their Consistency In An Extended Harvard Model

We demonstrate that the solar and atmospheric neutrino data as well as the recent result of the LSND experiment cannot be satisfied simultaneously with three light neutrinos if we consider the mass degeneracy for two neutrinos in the context of an extended Harvard Model based on the gauge group $SU(2)_{qL}\times {SU(2)}_{lL}\times {U(1)}_Y$ with $S_3\times Z_4$ discrete symmetry. Assuming two different representation contents under $S_3\times Z_4$ symmetry for pairwise neutrinos and the lone neutrino the present model admits neutrino masses of the order of 2.8 eV and can fit either solar and atmospheric neutrino data or the LSND and solar neutrino data.

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